<html>

  <body>

    <div class="main">
      <ul class="app"></ul>
    </div>

  </body>

  <script>

let app = document.querySelector('.app')
		let fragement = document.createDocumentFragment()
		for(let i = 0;i<5;i++){
			let div = document.createElement('li')
			div.setAttribute('class','item')
			div.innerText = 6666
			fragement.appendChild(div)
		}
		app.appendChild(fragement)




  </script>
</html>